The
special characteristics that enable plants and animals to be successful
in a particular environment are called adaptations.

Camouflage, as in a toad's ability to blend in with its
surroundings, is a common example of an adaptation. The combination of
bright orange and black on a monarch butterfly is an adaptation to warn
potential predators that the butterfly is poisonous and prevent it from
being eaten. These special features have evolved over long periods of time,
through the process of natural selection. Adaptations afford the organism
a better chance to survive in its surroundings.

Desert AdaptationsDeserts, where the environment is generally hot and extremely
dry, provide many striking examples of how plants and animals are adapted
to their surroundings. Plants have many adaptations
to cope with the lack of water. Some desert plants, such as the barrel
cactus, have expandable stems for storing water. Other plants have adaptations
that reduce water loss from their leaves, the part of a plant through which
most of the water is lost. Still others have a waxy coating on the leaves,
or have small leaves, that reduce the surface area exposed to the drying
elements. In many cases, desert plants have no leaves at all. Photosynthesis,
which normally occurs in green leaves, is carried out in the stems, which
are themselves green with the pigment chlorophyll.

Desert animals also have many adaptations
as well to help them survive in the desert climate. Many are nocturnal,
meaning active during the cool night rather than the hot daylight hours.
The kangaroo rat conserves water by excreting a solid urine rather than
liquid.

Tropical Rainforest AdaptationsIn sharp contrast, the climate of the tropical rainforest
is hot and wet. With over 80 inches of rain per year, as opposed to the
desert's 10 inches or less, plants have
adaptations
that enable them to shed water efficiently. The leaves of many rainforest
plants have drip tips for this purpose. Buttress and stilt roots are thought
to provide extra support for trees growing in spongy, wet soils.

Tropical rainforest plants also
have adaptations to take in what little sunlight is available on the dark
forest floor. Large leaves are common; they increase the amount of sunlight
a plant can capture. Other plants, like orchids, bromeliads and ferns,
grow as epiphytes
high up in the canopy where there is more sunlight.

Other AdaptationsThe adaptations discussed above
are all adaptations to specific climatic conditions, but organisms have
also developed adaptations to other aspects of their environment. Some
animals have adapted to eat a certain type of food; others have adapted
to avoid being eaten themselves. Most animals have behavioral adaptations
which help them attract a mate. In the plant world, many flowers
have evolved specific structures that help ensure pollination by the insects
they attract.